Caprock or
cap rock is a harder or more resistant
rock type overlying a weaker or less resistant rock type. Common types of caprock are
sandstone and
mafic rock types. In processes such as
scarp retreat, the caprock controls the rate of erosion of the scarp. As the softer rock is cut away, periodically the caprock shears off. Caprock is also found on the top of
mesa formations.